This invention relates to a single-crystal wafer having a superconductive ceramic thin film formed thereon for semiconductor devices, such as LSI's and Josephson devices.
Conventionally, attempts have been made to use as a material for semiconductor devices, such as LSI's and Josephson devices, a single-crystal wafer having a superconductive ceramic thin film formed thereon (hereinafter referred to as "a superconductive thin film-formed wafer"), which is prepared by forming a superconductive ceramic thin film (hereinafter referred to as "a superconductive thin film") containing as a main phase a crystalline phase having a composition by atomic ratio selected from the group consisting of Bi.sub.2 Sr.sub.2 Ca.sub.1 Cu.sub.2 O.sub.8 and Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.10 on a surface of a single-crystal wafer formed of Si, Ga--As, or the like by sputtering or PVD (physical vapor deposition) by the use of a target having a composition by atomic ratio selected from the group consisting of Bi.sub.2 Sr.sub.2 Ca.sub.1 Cu.sub.3 O.sub.10 and Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.4 O.sub.12, and then subjecting the resulting wafer to heat treatment under an oxygen atmosphere at a temperature of 890.degree. C..+-.2.degree. C. over 20 to 50 hours for crystalline orientation of the thin film.
Also, attempts have been made to use as a material for semiconductor devices, such as LSI's and Josephson devices, a superconductive thin film-formed wafer, which is prepared by forming a superconductive thin film containing as a main phase a crystalline phase having a composition by atomic ratio selected from the group consisting of Tl.sub.2 Ba.sub.2 Ca.sub.1 Cu.sub.2 O.sub.8, Tl.sub.2 Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.10, Tl.sub.1 Ba.sub.2 Ca.sub.1 Cu.sub.2 O.sub.7, Tl.sub.1 Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.9, and Tl.sub.1 Ba.sub.2 Ca.sub.3 Cu.sub.4 O.sub.11 on a surface of a single-crystal wafer formed of Si, Ga--As, or the like by sputtering or PVD (physical vapor deposition) by the use of a target having a composition by atomic ratio selected from the group consisting of Tl.sub.2 Ba.sub.2 Ca.sub.1 Cu.sub.3 O.sub.10, Tl.sub.2 Ba.sub.2 Ca.sub.2 Cu.sub.4 O.sub.12, Tl.sub.1 Ba.sub.2 Ca.sub.1 Cu.sub.3 O.sub.8, Tl.sub.1 Ba.sub.2 Ca.sub.2 Cu.sub.4 O.sub.10, and Tl.sub.1 Ba.sub.2 Ca.sub.3 Cu.sub.5 O.sub.12, and then subjecting the resulting wafer to heat treatment in an infrared oven under an atmosphere containing Tl vapor at a temperature of 900.degree. C..+-.2.degree. C. over 10 to 30 minutes, followed by quenching, for crystalline orientation of the thin film.
In the meanwhile, there is an increasing demand for a superconductive thin film to be formed on a single-crystal wafer, which has a still higher critical temperature (Tc) at which the film shows superconductivity, in order to cope with recent higher performance and increased wiring density of semiconductor devices.